PDP is usually prepared by baking metal electrodes, an insulating paste, a rib paste, etc. on a substrate glass at a temperature of from about 550 to 600° C., followed by frit-sealing the periphery together with a facing plate. As a substrate glass for PDP, it has been common to employ soda lime silica glass which is widely used in the field of buildings or automobiles.
However, the glass transition point of such soda lime silica glass is from 530 to 560° C. Therefore, if subjected to heat treatment at the above baking temperature, the substrate glass undergoes deformation or shrinkage and thus undergoes a substantial dimensional change, whereby it has been difficult to precisely align the electrode positions with the facing plate.
In order to solve such a problem of thermal deformation or thermal shrinkage of the substrate glass, a glass composition for substrates has been known which has a thermal expansion coefficient close to soda lime silica glass and which has a high glass transition point and a high strain point (Patent Document 1).    Patent Document 1: JP-A-8-165138